Hello,
I purchased a 1991 300e 3.0. I helped install a rebuilt trans and new suspension and exhaust. The car runs great for days. BUT every so often I say the car goes into stupid mode. The car starts to run rough and is down on power. The car will not take fuel very well and when you stop and then pull out the car shifts very hard. It may take 3 to 10 miles and then all of a sudden the car is back to normal runs great shifts very smooth. There is no check engine light at all. The car will run fine for days or maybe an hour and will do this again. The car has new plugs, wires, cap. I have checked the plug wires for continuity and they turned out fine. I have looked for lose connections but all looks good. I hope someone out there has seen this problem and can tell me what to look for???? Thanks

Change fuel filter(s) and report back.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Hello Skippy,
I will be replacing the fuel filter under the car Friday 12/12/14. Is there more than one filter? I only saw the one next to the fuel pump. Thanks

I think yours only has one, but I'm not sure. I'm more used to dealing with diesels, which tend to have two or even three.

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Whoever said there's nothing more expensive than a cheap Mercedes never had a cheap Jaguar.

83 300D Turbo with manual conversion, early W126 vented front rotors and H4 headlights 400,xxx miles
08 Suzuki GSX-R600 M4 Slip-on 22,xxx miles
88 Jaguar XJS V12 94,xxx miles. Work in progress.

Check the hose under your fuel distributor ... its in the lower center and comes toward the bumper. There are also 2 vacuum connection under it... on the far right as you stand in front of the car. I believe you can check them with a mirror.

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1985 300D 198K sold
1982 300D 202K
1989 300E 125K
1992 940T

"If you dont have time to do it safely, you dont have time to do it"

"The democracy will cease to exist when you take away from those who are willing to work and give to those who would not."

check all vacuum,and hoses from crankcase to.I changed my fuel pump,at 165,000 miles to be safe.

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1999 w140, quit voting to old, and to old to fight, a god damned veteran

The hard shift is a hint that there is low vacuum at the tranny vacuum modulator. Check it, and the lines and fittings going to it.

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Prost!

The low vacuum is just a symptom of the problem. Intermittant problems are almost always electrical. A clogged fuel filter cant "clear" and then "clog" again. Think about it.


Park the car, start it, hook up your voltmeter to check duty cycle and wait. Observe what happens when it starts to stumble and let us know what your readings were.

I had a similar issue, and I had to drive around for a week with my voltage tester riding shotgun. Once the stumble started, I pulled over and checked. Ended up being a loose ground.

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Eugene

10 E63 AMG
93 300te 4matic
07 BMW X3
14 Ford F-150 Fx2

Sounds like you may have a misfire. Slow to rev up during a misfire can cause the trans to shift hard, making it seem as though it may be a vacuum issue....See this all the time. Check your cap, rotor, plugs, and plug wires....Just a thought. oops, didn't see that you already addressed the ignition parts. Could also be a missfire from a bad fuel delivery.